Oil and gas wells often include lengths of tubular screen material at the lower section of the production tubing string to filter sand and other debris from the oil or gas produced. Often several lengths of screen are coupled to each other and to the tubing string. These couplings conventionally include tapered, interference type threads, and are formed with chrome and nickel alloy steels. This interference fit causes make-up problems and thread galling. With tapered, interference threads, it is difficult to achieve the initial coupling by hand, and the use of rig tongs is required. When it becomes necessary to remove and reinstall the coupling, interference threads tend to bind and tear.
In the past, non-tapered non-interference threads have been used in the direct coupling of high strength, heavy walled well casing sections for use in extremely long casing strings for deep, critical high pressure environments. These applications involve large diameter, thick walled tubing sections which are either directly threaded together or joined by a thin walled coupling member as exemplified by couplings developed by Hydril. Such couplings have not been considered to be feasible for small diameter, thin walled tubing such as that used in well screen section couplings.
It is a primary object of the present invention to provide a novel and improved well screen coupled connection which includes a two step coupled joint with non-tapered, non-interference threads.
A further object of the present invention is to provide a novel and improved well screen coupled connection with non-tapered, non-interference threads and positive metal-to-metal seals formed on the thin walled, small diameter coupling pins for well screen sections.
Another object of the present invention is to provide a novel and improved well screen section and coupling combination to facilitate suspension of a well screen section over a well head during manual coupling thereof with another well screen section.
These and other objects of the present invention are obtained by providing a well screen two step coupled connector and method which includes a well screen with a thin walled tubular pin having a constant diameter channel and three pin sections of successively increasing diameter. The end of the pin has an annular angled surface and an angled recess is provided between the intermediate and innermost pin sections, while non-inclined external threads are formed on the end and intermediate pin sections. A tubular open ended coupling is provided having a passage divided into two coupling sections by an inwardly projecting divider. Each coupling section is configured to receive the end and intermediate pin sections and includes non-inclined threads to mate with the pin section threads. The coupling includes an angled wall adjacent the divider to provide a seal with the annular angled surface at the end of the pin and an angled projection which fits within and forms a seal with the angled recess in the pin.